1. Field of the Invention
The present invention relates to an offset compensation circuit, and more particularly, to a circuit that can compensate for an offset value by inputting to the current-to-voltage converting circuit, a corrected reference voltage in which an offset value that may occur in the current-to-voltage converting circuit is reflected.
2. Description of the Related Art
In a photo diode integrated circuit (PDIC), an offset voltage is generated due to a physical device size mismatch, a current flowing through both input terminals of a current-to-voltage converter, and a leakage current occurring in a feedback resistor.
In the related art, in order to compensate for the offset voltage, a method of compensating the offset voltage by using a compensation resistor is used to reduce the amount of offset current flowing through the input terminals of the current-to-voltage converter.
FIG. 1 is a schematic view illustrating a current-to-voltage converting circuit according to the related art.
Referring to FIG. 1, a current-to-voltage converting circuit 100 according to the related art may include a photo diode integrated circuit 140, an amplifier 130, and a compensation resistor 110.
An output voltage V0 of the circuit is obtained by the following Equation.V0=ipRf+VREF+[(IB−)Rf−(IB+)RC]
The output voltage V0 may be calculated on the basis of a voltage ipRf obtained by using photocurrent ip generated by an external light source and a feedback resistor Rf, a reference voltage Vref, and an offset voltage Ib−Rf generated by leakage current generated from the feedback resistor Rf.
In order to compensate for the offset voltage, in the related art, the compensation resistor Rc is used to reduce the amount of offset current flowing through input terminals of the current-to-voltage converting circuit. In this way, the offset voltage is compensated.
However, according to the related art, the size of the compensation resistor Rc may be changed during a semiconductor process, and the voltage between both terminals of the photo diode may be changed to generate a new offset error.